Brazing of Ti-6Al-4V with a copper-based brazing filler metal

A copper-based (Cu-40Ag-6Ga-1Si, wt.%) filler metal was developed and used for Ti-6Al-4V brazing. The solidus temperature of the filler metal is 773.05 °C and the liquidus temperature is 776.14 °C. The spreading coefficient and contact angle of the filler metal at 850 °C on TC4 are 95.07% and 5°, respectively. The brazing experiment of Ti-6Al-4V (TC4) was performed using the copper-based filler metal. The TC4 alloy was successfully brazed using the Cu-Ag-Ga-Si filler metal at the brazing temperature 850 °C for 10 min. The joint microstructure consisted of αTi/TiCu and Ti2Cu IMCs/Cu(s,s), Ag(s,s), and AgCu eutectic. The effects of brazing time on the microstructure, shear strength, and microhardness of the brazed joints were investigated. The (Ti, Cu) intermetallic compound increased with time, which degrades the properties of the brazed joint. The shear strength of the brazed joint decreases with the increase of holding time. The average shear strength of the joint is 170.65 MPa at the brazing temperature of 850 °C for 10 min. The microhardness across the joint increases first and then decreases with the holding time. The average microhardnesses of the brazing center is 170.5  HV, and the maximum microhardness is 699.3 HV at the interlayer area due to the high content of intermetallic compounds. Further prolonging the holding time from 10 min is not beneficial for the joint strength.